Apparatus for producing press-molded articles

ABSTRACT

A combination provided in each compressing unit of a conventional rotary punch-and-die tablet forming machine, including an upper punch, a guide sleeve bearing the upper punch, an upper surface of a matrix having a die cavity and capable of forming a top airtight chamber encircling the upper punch when the sleeve reaches its lowest position, and a bottom airtight chamber formed by a recess formed in a rotational structure which is covered with the matrix and encircling a lower punch. Each of these components is employed in collaboration with a pressure regulating means mounted on a stationary frame portion of the machine coupled with a vacuum pump and capable of local and timed reduction of the pressure within each of said top and bottom airtight chambers, for effective production of press-molded articles.

United States Patent [72] Inventor Fumio Sato' A Hyoyo PreL, Japan [21 App]. No. 877,769 [22] Filed Nov. 18, 1969 [45] Patented Aug. 17, 1971 [32] Priority Nov. 18, 1968 U 1 7 Japan {31] 43/8 1292 54] APPARATUS FOR PRODUCING PRESS-MOLDED ARTICLES 10 Claims, 1 1 Drawing Figs.

52 U.S. c1 107/17,

' Y 25/67 [51] lnt.Cl. 1330b 11/10 [50] FieldofSearch "107/17, 15; 18/20; 25/69 [56] References Cited UNITED STATES PATENTS 2,043,08d 6/1936 Westin etal.

2,969,753 1 7-24, 6-bancho, Koshien, Nishinomlya-shi,

1/1961 Abbeetall 3,029,752 4/1962 Frank l07/l7X 107/17 Primary Examiner-Price C. Faw, Jr. 1 Attorney-Wenderoth, Lind & Ponack ABSTRACT: A combination provided in each compressing unit of 'a conventional rotary punch-and-die tablet forming v machine, including an upper punch, a guide sleeve bearing the upper punch, an upper surface of a matrix having a die cavity and capable of forming a top airtight chamber encircling the upper punch when the sleeve reaches its lowest position, and a bottom airtight chamber formed by a recess formed in a rotational structure which is covered with the matrix and encircling a lower punch Each of these components is employed in collaboration with a pressure regulating means mounted on a stationary frame portion of the machine coupled with a vacuum pump and capable of local and timed reduction of the pressure within each of said top and bottom airtight chambers,

for effective production of press-molded articles.

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INVENTOR FUM 1o SATO DY wwafdnd/ m ATTORIVEYS" APPARATUS FOR PRODUCING PRESS-MOLDED ARTICLES BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention generally relates to a novel manufacturing art of press-molded articles useful in the field of, for instance, pharmaceuticals, agricultural chemicals, foods, powder metallurgy, ceramics and the like. Particularly, the invention relates to a novel apparatus capable of advantageously carrying out a high-speed compressing operation which has hitherto been believed to have an adverse effect on the quality of the molded tablet articles.

2. Description of the Prior Art In manufacturing operation of the molded articles such as pharmaceutical or food tablets and the like, using a conventionally known dieand-punch type compressing machine, it is has been customary preferably to make the compressing velocity of the punches as low as possible as well as to prolong the dwelling period of the punches at their compacting extremes.

However, operational conditions involving the aforesaid customary operational mode inevitably conflict with the requisites of high-speed molding operation, and an advent of an art capable of producing excellent quality, press-molded articles at a high compressing velocity and a short compression dwelling period, has been long awaited.

The present invention may be adapted for use with conventional rotary tablet presses of the general type found or referred to in prior art U.S. Pat. Nos. 1,844,700; 2,846,723; 2,989,781; and 3,118,183.

The present inventor-applicant takes cognizance of the fact that a press-molding operation in vacuo produces a favorable effect on the quality of the molded articles, and has evolved the present novel apparatus after conducting lengthy research on the matter.

However, the placing of the whole press-molding apparatus in vacuo or in a reduced-atmospheric pressure is considered to be impractical in view of a stabilized continuous supply of raw material which generally takes the form of a powder or granular material which is liable to be scattered, a stabilization of the water content of the raw material and actual operation conditions on the one hand; and, on the other hand, it is considered that maintaining a machine which is an aggregate or composite of metal components within a high vacuum condition is difficult to achieve even locally in view of the balance between the accuracy of finishing of the machine, and the practicability and maintenance thereof.

The inventor has now discovered or determined the fact that there is no appreciable different in the qualitative aspect between the results obtained from the press-molding operation performed under a condition where the pressure is reduced to 2 mm. Hg abs. and that obtained from the operation performed under a condition where the pressure is reduced to 200 mm. Hg abs. at a compressing velocity which is generally considered to be an utmost within easy reach of an apparatus performing an ordinary compressing roller-type molding; and applicant has finally complete the present invention by providing an apparatus capable of performing local and timed reduction of the pressure to an extend such that it is easily realizable based on the above discovery.

SUMMARY OF THE INVENTION It is therefore the primary object of the present invention to evolve a high-speed press-molding operation without spoiling the quality of the molded articles. It is another object of the present invention to achieve a local reduction of the pressure inside the press-molding machine and a timed regulation of the reduction in a manner that does not affect the physical characteristics of the powder or granular material to be molded while simultaneously preventing scattering of the material. It is a further object of the present invention to provide an apparatus so constructed that it can accomplish the above described objects. It isstill another object of the present invention to provide an apparatus so constructed that such a local reduction of the pressure and the timed regulation of the reduction also be utilized as a scavenging operation in the vicinity of the lower punches, which operation is indispensable for the unobstructed reciprocating movement of the lower punches.

BRIEF DESCRIPTION OF THE DRAWINGS These and other objects of the present invention and attendant advantages thereof will be apparent to those who are DESCRIPTION OF THE PREFERRED EMBODIMENT According to the present invention, there is provided an improvement to be described in association with the conventional punch-and-die type press-molding apparatus, the latter of which normally includes, in combination, a stationary frame, a rotational structure comprising a turntable rotatably mounted-on said stationary frame, of which said rotational structure bears a multiplicity of annularly disposed compressing units each composed of a matrix having a die cavity,

and complementary upper and lower punches which correspond to and are operative within said cavity, said punches being transferable sequentially one behind the other in unison with said die cavity while traveling generally circular paths. An axial reciprocative movement of said upper and lower punches performs press-molding of a powder or granular material, with the major portions of said reciprocative movements being effected by operatable contact between the root portions of both punches and a corresponding pair or pairs of rollers mounted on said stationary frame.

The improvement therewith includes a bottom or lower airtight chamber composed of a recess formed in the rotational structure, covered with the matrix and encircling the lower punch, which chamber is connectable to a pressure-regulating means mounted on said stationary frame through suitable pipelines; and, a guide sleeve bearing the upper punch which sleeve itself is slidably received by the rotational structure, and together are capable of forming a top airtight chamber which is connectable to the pressure-regulating means through a suitable conduit or pipeline. The tip of both punches and the top surface of the matrix, when the sleeve lowers to its lowest position in each annularly disposed compressing unit, are operative in collaboration with said pressure-regulating means connected to a vacuum pump and capable of timed operation which can establish and maintain in both airtight chambers a reduced pressure condition. This reduced pressure condition is first effected in the bottom airtight chamber and then in the top airtight chamber, and continues throughout the completion of the press-molding operation. A circulation of air to the bottom airtight chamber for scavenging the chamber is also made possible after the completion of the press-molding operation.

In the following paragraphs, the present invention will be described in detail by way of example illustrated in the drawings, in which description the explanations regarding the members and portions of the apparatus which are similar to the conventionally known prior art, will be omitted.

In the drawings, FIGS. l-A-l-J illustrate in sequence a compressing unit comprising the essential members for performing press-molding operation. The illustrative unit is along the periphery of the rotational structure, with an assumption that the axis of rotation of saidrotational structure is disposed on the right side of each view, while other major constructional components, operational mechanism, and the like of the basic rotational structure as well as the auxiliary equipment associated therewith, is not shown because they are generally of a type well-known in the prior art press-molding apparatus and are obvious to those who are conversant with the art to which the present invention pertains.

Through each view AJ of FIG. 1, an upper punch 6, a guide sleeve 2 bearing the upper punch, a receptacle 11 for the sleeve having an annular recess 17, a matrix 3 having a die cavity, a receptacle 12 for the matrix, a lower punch 4, a slide guide portion 13 for the lower punch and a recess 8 are provided coaxially along a vertical axis line which is parallel with the center axis of the rotational structure 1 and has a constant distance from said axis. The operating fluid conduits or pipelines 14, 15 and 16 for connecting the recesses with a pressure-regulating means 5 are formed within the rotational structure 1. The arrows indicate the directions of the flow of the air.

The guide sleeve 2 holds the upper punch 6 and is allowed a lengthwise movement effected by an annular guide rail (not shown) normally disposed against the receptacle 11, and said upper punch 6 has one or more vertically spaced O-rings designated inserted between it and sleeve 2, and between sleeve 2 and sleeve holder 11, so that airtight conditions are maintained between these components. Basically, there is no difference between the apparatus of the present invention and one of conventional prior art in the function of producing press-molded articles insofar as the upper punch 6 is designed to be vertically reciprocatively driven by a top roller and a top guide rail (not shown) while the rotational structure rotates, and the sleeve 2 provided for the purpose of holding the upper punch 6 is also designed to be vertically driven by a separately equipped guide rail (not shown).

The sleeve 2 forms an annular cylindrical space 22 around the upper punch 6 with its skirt (lower portion) 21, which skirt and annular space 22 are defined so as to form a top airtight chamber together with the upper surface of the matrix 3, when the sleeve is at its lowest position, with the help of a flexible boot 7 of rubber or synthetic resin covering an end flange 23 ofthe skirt 21.

Moreover, said annular cylindrical space 22 which forms said top airtight chamber 22 is communicated to an annular recess 17 formed in the bore of the sleeve receptacle 11 through openings 24 perforated on the sidewall of the sleeve 2, and said recess 17 is further connected to the pressure regulating means via control disc 9 through the conduit or pipeline 14.

On the other hand, the slide guide portion 13 of the rotational structure 1 supports the lower punch 4 permitting its lengthwise movement while maintaining an airtight condition therebetween with an Oring O. The upper portion of said guide portion 13 is formed with a recess 8, and it is covered with the matrix 3 to form an annular cylindrical space which serves as a bottom airtight chamber because the operative head of the lower punch 4 is always inserted within the die cavity of the matrix 3 while leaving a clearance which allows lengthwise movement of said punch 4.

Said airtight chamber is connected to the pressure-regulating means 5 via the conduits 15 and 16. The lower punch 4 is designed to be driven reciprocatively by a bottom roller and the-guide rail (not shown) in a similarmanner as has previously been described relative to the upper punch 6 and the sleeve 2.

As previously described, the top and bottom airtight chambers function in association with the pressure-regulating means 5, a nonrotating component, and the internal pressures of them will be reduced or open to the atmosphere on a timed schedule brought by the relative position of the rotational structure against the pressure-regulating means.

And this timed pressure regulation is performed by the control disc 9 which forms a part of said means and functions together with it, and is further maintained in a sliding contact with the rotational structure. The function of the pressureregulating means 5 including the control disc 9 is illustrated in FIG. 2, wherein at each angular position of the control disc 9 is shown and designated by a letter which corresponds to each of the operational conditions of the compressing units shown in FIGS. l-A-l-J. In other words, letters designating respective views of FIG. 1 correspond to the angular positions represented by the same letters in FIG. 2, and each position is being sequentially transferred in the direction of the arrow.

In the following paragraphs, the functions of the means and the compressing units will be described while relatedly referring to both views.

In the drawings, the condition in FIG. I-A represents a position of the components of the unit where a completed compression molding operation has taken place and the molded article cleared away, and wherein top airtight chamber 22 has not yet been formed and the bottom airtight chamber 8 is subjected to a slight reduction of pressure by suction of the air through the pipeline 15 with the other pipeline 16 open to the atmosphere. Therefore, a flow of air occurs in scavenge the residual powder or granular material, dust and the like away from the chamber as depicted by the arrows and said flow continues until immediately before condition C which will be later described. In condition B, the lower punch 4 is depressed to its lowest granular by the unshown guide rail and the powder or granular material 31 to be molded is charged into the die cavi ty of the matrix 3 through a hopper 30.

When said charging is completed, the lower punch begins to rise and when it reaches a given position shown in FIG. l-C, a surplus portion of the powder orgranular material 33 which exceeds the desired amount is scraped away by a suitable scraper 32. At this time, the flow of air circulating through the bottom airtight chamber is stopped.

In the next sequential condition of FIG. l-D, the lower punch 4 retracts again and at the same time the upper punch 6 and the sleeve 2 begin to descend. A regular reduction of the pressure inside the bottom airtight chamber 8 begins through both pipelines l5 and 16 after the condition of FIG. 1-E has been reached where both the lower punch 4 and the sleeve 2 reach their lowest position.

Said reduction of the pressure brings a suction of the air contained in the powder or granular material in the die cavity and an exhaustion of the powder or granular material which leaks out from the die cavity into the airtight chamber 8. Furthermore, it also serves for a preparatory containment or compacting of said powdered material 31 in the cavity and continues up to condition G where the full compression molding operation is completed.

It is to be remembered that the upper punch 6 and the sleeve 2 have already begun to descend commencing with the condition of FIG. 1-C, and when the latter (sleeve) reaches its lowest position shown at condition FIG. 1-E, the top airtight chamber 22 is formed. Although the reduction of the pressure within the bottom airtight chamber has already begun at condition shown in FIG. 1-E, the pressure reduction within the top airtight chamber 22 begins after the condition of FIG. l-F has been reached. In other words, the apparatus is designed so that the upper airtight chamber 22 will not be subjected to a reduction of pressure prior to that of the bottom or lower airtight chamber, because there is a possibility of scattering the powder or granular material 31 disposed within the die cavity, upwardly by suction if the reduction of the pressure of the upper airtight chamber beings prior to that of the bottom.

The compression molding operation involving a regular exertion of pressure by rollers (not shown) against the upper the lower punches is performed as illustrated in FIG. l-G where both airtight chambers are subjected to the regular reduction of pressure. When the compression molding operation is completed as in FIG. l-I-I, both of the airtight chambers are open to the atmosphere and airtight chambers are open to the atmosphere and air flows in, and the upper punch begins to I rise. Next, the sleeve 2 and the lower punch 4 begin to rise in sequence, and when the upper punch 6 and the sleeve 2 ascend to the highest position (through position shown in FIGS. 1-1 and lJ), the lower punch 4 effects the molded article 31' to bring it up over the upper surface of the matrix 3 where it is swept away by a deflector 34 as the lower punch 4 reaches its highest position.

In the described manner, the material is compressed into a tablet form article of the intended size and shape, and the illustrated compressing unit which is designed to repeat the identical operation with the rotation of the rotational structure returns to its initial condition, i. e. shown in FIG. l-A.

In this embodiment, the pressure-regulating means 5 is conventionally connected to a conventional vacuum pump (not shown) and the control disc 9 interposed between the means and the rotational structure is made of a material having a small coefficient of friction. Moreover, arc-shaped openings 2, Y and Z perforated herein are preferably maintained at -a vacuum below 200 mm. Hg abs., an atmospheric pressure and a slight reduction of pressure, respectively. Maintaining confined portions of a machine of ordinary accuracy of finishing, in a condition of reduced pressure to such an extent is not difficult to achieve, and although the O-rings are employed for maintaining the airtightness in this particular embodiment, other suitable means such as piston rings also can be advantageously employed. 1

Moreover, although portions of the conduits or pipelines are depicted by the dotted lines in FIGS. l-A, 1-B and 1-1, for the purpose of indicating these being connected to the atmosphere at these conditions, it is apparent that other suitable means can be applicable for establishing the connection.

As previously described, by utilizing the apparatus of the present invention, production of the press-molded articles under reduced pressure is achieved without any difiiculty and molded articles of excellent quality are obtainable using a high-speed compression under a condition of timed and local reduction of pressure, and therefore the apparatus has a unique advantage for improving the productivity.

1 claim:

1. In an apparatus for producing press-molded articles such as tablets from powdered material, comprising a generally conventional frame-supported rotary press-molding machine having a rotary head with a plurality of circumferentially disposed compressing units including a matrix with die cavity, and vertically reciprocating upper and lower punches with compressing ends cooperating with said cavity, the improvement comprising:

a. means in association with each of said compressing units for establishing and maintaining in timed sequence a vacuum adjacent said die cavity and adjacent portions of the respective punches during the compression molding operation;

b. said means for establishing and maintaining the vacuum include:

1. means defining airtight chambers adjacent the compressing ends of said respective upper and lower punches;

2. pressure-regulating means mounted on said machine frame; and

3. conduit means connecting the pressure-regulating means with a vacuum-producing source, and also with said respective punch airtight chambers; and

means for sequentially establishing and maintaining a reduced pressure condition of the vacuum in said respective airtight chambers in the order of thelower punch chamber first and then subsequently in the upper punch chamber.

2. The apparatus as defined in claim 1 further including means for circulating scavenging air to the lower punch chamber after completion of the molding operation.

3. Press-molding apparatus as defined in claim 1 wherein said vacuum chambers are made airtight by use of seals between the relatively movable upper and lower punches and their guide and support means respectively.

4. Press-molding apparatus as defined in claim 1 wherein the pressure-regulating means of paragraph (b) (2) includes an annular control disc having predetennined positioned,

generally arcuate openings therein for predetermined timed sequential interconnection of the vacuum chambers with the vacuum source, responsive to rotation of the rotational structure during molding operations.

5. in an apparatus for producing press-molded articles from powdered or granular material to be molded which includes generally the conventional combination of a stationary frame, a rotational structure comprising a turntable rotatably mounted on said stationary frame; said rotational structure bearing a multiplicity of annularly disposed compressing units with each including a matrix having a die cavity; complementary upper and lower punches each having root and compressing tip ends and each of which corresponds to and is operative within said die cavity and being transferable one behind the other in unison with said die cavity while traveling generally circular paths; means for effecting axial reciprocative movements of said upper and lower punches to effect press-molding of said material to be molded with the major portions of said reciprocative movements being effected by engagement of the root ends of said complementary punches with surfaces of at least a corresponding pair of rollers mounted on said stationary frame; the improvement compris-' ing in combination therewith, means for molding within a vacuum, by including in each of the annularly disposed compressing units means defining a lower airtight vacuum chamber recessed within the rotational structure, and covered with said matrix; said lower chamber encircling the lower punch; a pressure-regulating means mounted on said stationary frame and connectable with a vacuum source; conduit means interconnecting said lower chamber with said pressureregulating means; a generally vertically disposed guide sleeve bearing the upper punch; means slidably mounting said guide sleeve for the upper punch within said rotational structure; means on a lower portion of said guide sleeve capable of forming an upper airtight vacuum chamber encloseable around the tips of both punches, in combination with the top surface of the matrix;-conduit means for interconnecting said upper chamber to the pressure-regulating means responsive to means activated when said guide sleeve descends to its lowest position; said punches being operative to effect the press molding in collaboration with said pressure-regulating means which is connected to the vacuum source, and including means for effecting timed operation thereof which can sequentially establish and maintain in both of the airtight chambers a reduced pressure condition, with means for reducing the pressure condition first in the lower airtight chamber and substantially in the upper airtight chamber.

6. Press-molding apparatus as defined in claim 5 further including means for circulating air to the lower airtight chamber for scavenging the chamber after the completion of the pressmolding operation.

7. Press-molding apparatus as defined in claim 5 wherein said vacuum chambers are made airtight by use of seals between the relatively movable upper and lower punches and their guide and support means respectively.

8. Press-molding apparatus as defined in claim 5 wherein the conduit means interconnecting the respective upper and lower vacuum chambers with the pressure-regulating means are formed within the rotational structure.

9. Press-molding apparatus as defined in claim 5 wherein the pressure-regulating means includes an annular control disc having predetermined positioned, generally arcuate openings therein for predetermined timed sequential interconnection of the vacuum chambers with the vacuum source, responsive to rotation of the rotation structure during molding operations.

10. Press-molding molding apparatus as defined in claim 5 wherein the means on the lower portion of said guide sleeve for forming the upper airtight vacuum chamber includes a flexible annular boot mounted thereon. 

1. In an apparatus for producing press-molded articles such as tablets from powdered material, comprising a generally conventional frame-supported rotary press-molding machine having a rotary head with a plurality of circumferentially disposed compressing units including a matrix with die cavity, and vertically reciprocating upper and lower punches with compressing ends cooperating with said cavity, the improvement comprising: a. means in association with each of said compressing units for establishing and maintaining in timed sequence a vacuum adjacent said die cavity and adjacent portions of the respective punches during the compression molding operation; b. said means for establishing and maintaining the vacuum include:
 1. means defining airtight chambers adjacent the compressing ends of said respective upper and lower punches;
 2. pressure-regulating means mounted on said machine frame; and
 3. conduit means connecting the pressure-regulating means with a vacuum-producing source, and also with said respective punch airtight chambers; and c. means for sequentially establishing and maintaining a reduced pressure condition of the vacuum in said respective airtight chambers in the order of the lower punch chamber first and then subsequently in the upper punch chamber.
 2. pressure-regulating means mounted on said machine frame; and
 2. The apparatus as defined in claim 1 further including means for circulating scavenging air to the lower punch chamber after completion of the molding operation.
 3. conduit means connecting the pressure-regulating means with a vacuum-producing source, and also with said respective punch airtight chambers; and c. means for sequentially establishing and maintaining a reduced pressure condition of the vacuum in said respective airtight chambers in the order of the lower punch chamber first and then subsequently in the upper punch chamber.
 3. Press-molding apparatus as defined in claim 1 wherein said vacuum chambers are made airtight by use of seals between the relatively movable upper and lower punches and their guide and support means respectively.
 4. Press-molding apparatus as defined in claim 1 wherein the pressure-regulating means of paragraph (b) (2) includes an annular control disc having predetermined positioned, generally arcuate openings therein for predetermined timed sequential interconnection of the vacuum chambers with the vacuum source, responsive to rotation of the rotational structure during molding operations.
 5. In an apparatus for producing press-molded articles from powdered or granular material to be molded which includes generally the conventional combination of a stationary frame, a rotational structure comprising a turntable rotatably mounted on said stationary frame; said rotational structure bearing a multiplicity of annularly disposed compressing units with each including a matrix having a die cavity; complementary upper and lower punches each having root and compressing tip ends and each of which corresponds to and is operative within said die cavity and being transferable one behind the other in unison with said die cavity while traveling generally circular paths; means for effecting axial reciprocative movements of said upper and lower punches to effect press-molding of said material to be molded with the major portions of said reciprocative movements being effected by engagement of the root ends of said complementary punches with surfaces of at least a corresponding pair of rollers mounted on said stationary frame; the improvement comprising in combination therewith, means for molding within a vacuum, by including in each of the annularly disposed compressing units means defining a lower airtight vacuum chamber recessed within the rotational structure, and covered with said matrix; said lower chamber encircling the lower punch; a pressure-regulating means mounted on said stationary frame and connectable with a vacuum source; conduit means interconnecting said lower chamber with said pressure-regulating means; a generally vertically disposed guide sleeve bearing the upper punch; means slidably mounting said guide sleeve for the upper punch within said rotational structure; means on a lower portion of said guide sleeve capable of forming an upper airtight vacuum chamber encloseable around the tips of both punches, in combination with the top surface of the matrix; conduit means for inteRconnecting said upper chamber to the pressure-regulating means responsive to means activated when said guide sleeve descends to its lowest position; said punches being operative to effect the press molding in collaboration with said pressure-regulating means which is connected to the vacuum source, and including means for effecting timed operation thereof which can sequentially establish and maintain in both of the airtight chambers a reduced pressure condition, with means for reducing the pressure condition first in the lower airtight chamber and substantially in the upper airtight chamber.
 6. Press-molding apparatus as defined in claim 5 further including means for circulating air to the lower airtight chamber for scavenging the chamber after the completion of the press-molding operation.
 7. Press-molding apparatus as defined in claim 5 wherein said vacuum chambers are made airtight by use of seals between the relatively movable upper and lower punches and their guide and support means respectively.
 8. Press-molding apparatus as defined in claim 5 wherein the conduit means interconnecting the respective upper and lower vacuum chambers with the pressure-regulating means are formed within the rotational structure.
 9. Press-molding apparatus as defined in claim 5 wherein the pressure-regulating means includes an annular control disc having predetermined positioned, generally arcuate openings therein for predetermined timed sequential interconnection of the vacuum chambers with the vacuum source, responsive to rotation of the rotation structure during molding operations.
 10. Press-molding molding apparatus as defined in claim 5 wherein the means on the lower portion of said guide sleeve for forming the upper airtight vacuum chamber includes a flexible annular boot mounted thereon. 